CRUSTACEA OF THE MERGUI ARCHIPELAGO. bY. 
obtuse angle with the anterior declivity of the gastricregion. In 
_H. Pleione, on the contrary, the spines are directed more down- 
wards, so that they are situated in the prolongation of the oblique 
surface of the anterior declivity of the gastric region. When the 
tips of the two rostral spines are united by an imaginary line 
and the antero-internal angles of the supraorbital margins by 
another, the proportion of the distance between these two 
imaginary lines to the distance between the antero-internal angles 
of the supraorbital margins is as 8 to 3; in the smaller female 
individuals this proportion is as 5 to 8, because the rostral 
spines are comparatively shorter. The basal antennal joint is a 
little narrower in this species than in H. Plecone, and its external 
margin is also of a somewhat different shape. In Herbst’s 
species the epistome is comparatively a little shorter, and it there- 
fore appears a little more enlarged; in this species (the male) 
the epistome is 13 millim. long, and the distance between the 
postero-internal angles of the orbits is 44 millim., and therefore 
three times as broad as the length of the epistome. Immediately 
behind the postero-internal orbital angles a small dentiform 
tubercle is found, lying between these angles and the antero- 
external angles of the buccal cavity. The penultimate joint of 
the peduncle of the external antenne is twice as long as the ter- 
minal joint. The outer maxillipeds and the male abdomen much 
resemble those of AH. oryx. 
The chelipedes are scarcely longer than the length of the 
body (the spines of the rostrum included). The upper margin 
of the arm is provided above, at the proximal extremity, with two 
dentiform tubercles situated very near to one another. The 
wrist presents a small tubercle at its internal angle, and one 
or two on its upper surface. The hands are rather slender, 
being nearly five times as long as high, the fingers (which are 
about half as long as the palm) included. The scarcely sinuous 
upper and under margins of the palm are parallel to one 
another ; the hands are quite smooth and glabrous. The inner 
edges of the fingers are minutely denticulate and a little gaping 
at the base. 
The ambulatory legs much resemble those of H. oryx. Those 
of the first pair are about once and a half as long as the whole 
body, and the other legs are successively shorter ; so that the 
ambulatory legs of the last pair are only once and one third the 
length of the cephalothorax (exclusive of the aa apres 
LINN. JOURN.— ZOOLOGY, VOL. XXII. 2 
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